pub fn new_birthday_probability(n: u32) -> f64 {
    if n > 365 {
        return 1.0;
    }
    let mut prob = 1.0;
    for i in 0..n {
        prob *= (365 - i) as f64 / 365f64;
    }
    let res: f64 = format!("{:.4}", 1f64 - prob).parse().unwrap();
    res
}
